Spotting the member of a rival gang in Central City last year, Tyron Harden allegedly aimed an AK-47 at that person and pulled the trigger. He ended up hitting a 5-year-old girl, Briana Allen, and killing her, the New Orleans Police Department alleges.

After speaking to numerous people with knowledge of the incident, authorities jailed Harden on Monday in connection with the murders of Briana Allen and Shawanna Pierce, 33, who happened to be driving through the area at the time of the shooting. Police also booked Harden with conspiring to murder three people who were wounded on the day Briana and Pierce were shot, including a 10-year-old boy.

According to investigators, on May 29, 2012, a crowd of people had gathered in the 1200 block of Simon Bolivar Avenue to celebrate a boy's 10th birthday party when Harden and two other men ran toward the crowd, spraying bullets. The attackers then retreated into a car they had parked nearby and drove off.

Harden, 19, wielded an AK-47, and the other two had handguns, police allege. Police said a surveillance camera captured video of the men parking the car, getting out, firing guns at the crowd and leaving.

Briana, a relative of the birthday boy, and Pierce, who was on her way to return a rental car in the Central Business District, died at the hospital after being shot. The birthday boy as well as Briana's uncle were among those wounded.

An hour or so after the shootings, Harden and his accomplices met up with several people and bragged about what they had done within earshot of at least three witnesses, police say. One of the witnesses claimed an accomplice of Harden's laughingly boasted, "I killed a whole baby!"

That witness didn't immediately understand what the accomplice was referring to, but then he watched a news report about the killings and understood.

Police allege that one of the accomplices subsequently told several people that he and Harden were involved in the slayings of Briana and Pierce. That accomplice said the murder of the "baby" was a mistake -- Briana was not the intended target, though Harden shot her as he tried to cut down a rival gang member who was running away from the attack at the party, police state in court papers.

The papers do not name either the alleged accomplice or the gang member being targeted. However, one suspect had been charged in the case before Harden's arrest: Leo Riles, 19, who surrendered within hours of the shootings and was indicted in August on two counts of first-degree murder. And New Orleans Police Superintendent Ronal Serpas has previously said that the targets of the attack on Simon Bolivar Avenue were Briana's uncle and the other man who was injured.

On Friday morning, NOPD Homicide Detective Ryan Vaught obtained a warrant to arrest Harden. By 11:07 a.m. Monday, Harden had been booked with two counts of first-degree murder and three counts of conspiracy to commit attempted first-degree murder.

First-degree murder convictions carry life imprisonment or the death penalty.

NOPD officials on Monday said Harden is a known member of the Young Mafia Fellaz street gang and is an associate of a group called the 110'ers, formed from three smaller neighborhood clans in the 10th Ward. Authorities have previously said they believe the 110'ers were responsible for the shootings that killed Briana and Pierce.

Serpas said police officials expect to make more arrests in the case, which was investigated by various NOPD units, the FBI, the Orleans Parish district attorney's office and the Bureau of Alcohol, Tobacco, Firearms and Explosives.

"I want to commend our homicide detectives for piecing together this unthinkable crime, which involved gunmen actually planning to strike at a child's birthday party because they knew it would be an easily accessed event, and they'd have ample opportunity to hit their desired target," the police chief wrote in a statement. "These men didn't care that they might end up killing one child and wounding another during their attempt, and that's unconscionable."

This is not the first time Harden has been accused of a violent crime. In August 2011, he allegedly ran a stop sign at Churchill Drive and Paris Avenue in a white Chevrolet Camaro and began fleeing from officers who tried to pull him over. Harden crashed into a car in the 4300 block of Touro Street, bailed and ran into an alley, police said. He allegedly removed a .40-caliber pistol with an extended magazine containing 29 rounds from his waistband, threw it onto the ground and jumped over several metal fences.

Police said they apprehended Harden in a yard in the 2000 block of Stephen Girard Street. He was booked with aggravated flight from an officer, illegal carrying of a weapon and unauthorized use of a motor vehicle because the Camaro was a rental car he allegedly did not have permission to drive.

At the time of that arrest, for which he is awaiting trial, Harden was wearing an electronic ankle bracelet while being monitored in relation to an unrelated armed robbery charge. The armed robbery charge was ultimately dropped.

On Monday, Harden's attorney, Gregory Carter, described the allegations against his client as "completely out of character for him and his family for that matter."

"We're just looking forward to getting to the bottom of things," Carter said. "It's just not in his character. His family has been his backbone of support."